Multiple output AC/DC converter with an internal DC UPS

The usual way to avoid a computer shutdown during a mains failure is to connect an ac uninterruptible power system (UPS). However, there are other possibilities, such as using a dc UPS to obtain the dc output voltages directly from the battery instead of generating an ac voltage to feed the whole power supply. Thus, the topology must operate either from the ac mains or from a battery. A complete design of an ac/dc power supply with an internal dc UPS is presented in this paper. The solution is based on the coupling of the UPS to the main transformer. Moreover, the power supply meets all the requirements needed to be used as an Advanced Technology eXtended (ATX) PC power supply-multiple outputs, power and voltage ratings, size, protections, etc. A prototype has been fully developed and tested as a PC power supply. The autonomy achieved at full power is around 7 minutes.